1. The Field of the Invention
The present invention relates to a process for the preparation of 2,3-dimethylphenol and of 3,4-dimethylphenol. More particularly, the invention relates to a process in which the said compounds are prepared by hydrolysis of the corresponding bromobenzenes in an aqueous solution, to yield the desired product with high purity and yield.
2. The Prior Art
Dimethylphenols are useful intermediates in the synthesis of a variety of organic compounds, particularly in the preparation of polymers. Preparation of these compounds has been attempted by various routes in the art. For instance [FR 1,580,963; Czech Pat. 159,637; USSR 577202], sulphonation of xylene and subsequent hydrolysis has been carried out. In another process, xylene was brominated then aminated and diazotized. A diazo compound was decomposed to form the desired product [Z. N. Lavrova et al, C.A. 76: 33912w (1972)]. Alternative methods employed were the nitration of xylene [C.A. 70: 106432c (1969)], the oxidation of xylene with a peroxide [U.S. Pat. No. 3,377,386] and the hydrolysis of 3,4-dimethylanisole [C.A. 52: 14563d (1958)].
However, the processes of the art present several disadvantages. For instance, sulphonation is a less selective process than bromination, and hydrolysis thereof must be carried out under conditions which are more extreme than those required for the hydrolysis of bromides (usually at temperatures higher than 300.degree. C. and for relatively longer periods of time). Aminating and then diazotizing, on the other hand, is not a convenient procedure because one extra step, as compared with the hydrolysis route, is required, and diazotization normally results in lower yields than hydrolysis. Nitration is a relatively non-selective reaction, which leads to considerable waste of by-products.
It is therefore clear that it would be highly desirable to provide a simple, efficient and highly specific process which overcomes the drawbacks of the processes of the present art.